System for locating a radiant-signal reflector



3 Sheets-Sheet 1 H. M. LEWIS SYSTEM FOR LOCATING A RADIANT-SIGNALREFLECTOR Filed March 26, 1948 May 2, 1961 5 Sheets-Sheet 2 H. M. LEWISSYSTEM FOR LOCATING A RADIANT-SIGNAL REFLECTOR May 2, 1961 Filed March26, 1948 SYSTEM FOR LOCATING A RADIANT-SIGNAL REFLECTOR H. M. LEWIS 3Sheets-Sheet 3 May 2, 1961 Filed March 2 SYSTEM FoR LocATlNG ARADIANr-SIGNAL REFLECTOR Harold M. Lewis, Allenhursf, NJ., signor toHazelalie v This invention relatesto systems for locating aradiant-signal reflector. More particularly, the invention is directedto systems for Ascanning a predetermined space with a sharplyconcentrated radiant-signal beam and for receiving andI utilizing theradiant-signal energy of the beam reilectedby a reector, such as anaircraft, in the path of the beam to provide an indication of thedistance and the direction of the reflector from the system.

Aircraft-locating systems heretofore employed have scanned apredetermined space in either one or two directions with a concentratedradiant beamof wave signals and have utilized the reected wave-signalenergy received from an aircraft in the path of the beam to produceanfindication representative of the distance and the direction of theaircraft from the locating system. Certain prior suchsystems haveaccomplished this by the use of a radiant-signal translating systemhaving a radiating characteristic in the form of a concentrated beam,the

advantages inherent in systems wherein the movement of the scanning beamis produced' mechanically. One such type of loc'ating system utilizesone or more arrays of physically spaced radiant-signal translators,which are /scanningactiom thus avoiding the above-mentioned disccoupled to a common Wavefsignalftranslating channel throughindividuallphase-shifting 'devices Vandenergized rfrom an end oneof the'translators by wave-signal energy l `of changing frequency.v A systemofthis type forms the subject matter of. United States Letters PatentNo.

2,407,169, granted September 3, 1946, to Arthur V.

Loughren, entitled System For i Locating Radiated- SignalReliectorsfandassigned to theesame assignee as the present invention.

- vAnother prior such locatingV system wherein scanning vby theradiant-signal beam is` accomplished electricallyA hasemployed acarrier-frequency wave-signali generator, one or more wavesignalgeneratorsE whichA determine Vthe scanning frequencyof the `radiantbeam, a heterodyne oscillator, and numerous band-pass selectors,modulators, 6

and amplifiers for developing wave signals of the proper frequency forapplication to 'and radiation by individual ones of a plurality rofspaced lwave-signal translators. Generally 'similar units are alsoemployed in the receiver portion of this locating system in order toutilize the reflected wave-signal energy .to provide an indication ofthe presence inthescanned area'of a Wave-signal reflector such'as anaircraft. Systems of the type just mentioned form the Vsubject matter ofapplicants United States Letters -Patent No.4 2,426,460, granted August26,11947, lentitled SystemForLoca'ting`A `a Radiated-Si'gnal Retiel2,982,957 Patented May 2, 1961 "ice tor; United States Letters PatentNo. 2,429,726, granted October 28, 1947, entitled System ForSpace-Scanning With a RadiatedWave-Signal Beam; and United StatesLetters Patent No. 2,430,296, granted November 4, 1947, entitledRadiated-Signal Receiving System, all assigned to the same assignee asthe present invention. Since a relatively large number of circuitelements and units are v ordinarily used in a locating system of thetype just Yreferred to, the system may be somewhat complex for certainapplications. A locating system of the type disclosed in applicantsabove-identified patents is particularly suited for rapid angularscanning. In a particular application, however, it may be desired thatthe scanning be accomplished ata relatively slow rate. In such event,the frequencies selected by the band-pass selectors are more closelyspaced and the selectors are then designed and adjusted with somewhatgreater care. It may also be desirable to alter over a wide range ofvalues the rate at `which the scanning operation preceeds from time totime'. Systems of the type last described involve readjustments ofnumerous band-pass selectors to accommodate such changes of scanningrate over a wide range and may thus limit somewhat the rapidity withwhich large changes of scanning rate may be accomplished.

It is an object of the invention, therefore, to provide a Vnew andimproved system for eifecting electrical scanning to locate aradiant-signal reiiector.

It is another object of the invention to provide a new and improvedsystem for locating a radiant-signal reiiector, Which scans apredetermined space entirelyby electrical means yet is relatively simplein construction.

' It is a further object of the invention to provide a new and improvedsystem for locating a radiant-signal reflector which requires the use ofonly a very limited number of wave-signal selectors.

It is yet another object of the invention to provide a new and improvedlocating system which is particularly suited for operation with pulsemodulation.

It is another object of the invention to provide anew and improvedsystem for locating a wave-signal reilector which utilizes the sameradiant-signal translators for both transmitting and receivingwave-signal energy.

It is an additional object of the invention to provide a new andimproved system for scanning a predetermined .space with apulse-modulated radiant-signal beam.

In accordance with one form of the invention, a system Vfor scanning apredetermined space with a radiant-signal beam comprises a plurality ofspaced signal radiators, mea'ns for'providing two lcarrier-frequencywave signals having a substantially quadrature phase relationship, and-means for Yproviding two signals having a substantially quadraturephase relationship and having a frequency Vrelated to the desiredfrequency of Scanning of the space by the radiant-signal beam; The.systemalso includes modulator means responsive to the above-mentionedWave signals and signals for', deriving at least two wave-signalmodulation components vof different frequencies whereby the systemangularly scans the predetermined space with the radiant-signal beam.

. Alsof in accordance with the invention, 'a-system for 'locating avradiant-signal reilectorrby scanning a predetermiried space duringalternate or transmitting 'intervals `with a'pulse-modulated beamincludes the scanning system just mentioned and alwave-si'gnal receiver`including a plurality of heterodynemodulators coupled to individualones of the plurality of spaced radiators or translators. 4The modulatormeans of the locating system is eiective :tol derive and'to apply to theheterodyne modulators -dring iterveningor receiving intervals individualVones :of a plurality of .wave-signal I modulation components ofindividual frequencies different from each other and from the,components mentioned in the precedingv paragraph.

frequency during intervening intervals.

3. This is to enable the locating system angularly to scan the aforesaidpredetermined space with a pulse-modulated radiant-signal beam andradiant-signal energy of the beam reflected `by any radiant-signal`reflector inthe predetermined space to the translators produces in theheterodyne modulators modulation components Ahaving additive phase onlyfor one direction of reception bythe translators, which direction scansthe predetermined space effectively in synchronism with theradiant-signal beam. The locating system further includes means forutilizing the above-mentioned additive-phasemodulation components toprovide an indication of at least the direction of the reflector withrespect tothe system.

For a better understanding of the` present invention, together withother and further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawings, and its`scope will be pointed out in the appended claims.

Referring now to the drawings, Figs. 1 and 1A represent, partlyschematically, when placed in adjoining relationship along theirrespective broken lines A-A and `with the corresponding circuits a-z',inclusive, in alignrment a complete system for locating a radiant-signalre- `iiector embodying the invention in a particular form; and Fig. 2represents, also partly schematically, a complete locating systemembodying the present invention in a modified form.

Referring now more particularly to Figs. 1 and 1A of the drawings, thesystem for locating a radiant-signal reector there represented comprisesaplurality of spaced, directive, signal `translators `or antennasV 11,1,1', 1.2, -and 12". These antennas are preferably linearly aligned `andequally spaced. The directivity may beincreased by the provision ofdirective elements, such asretlectors `13, 13 of suitable length and ofsuitable spacing from the antennas. For the particular embodimentrepresent- `ed in Fig. 1, an odd number of antennas are employed andthese have a spacing `which is determined by the size of the desiredsector or angle to be scanned. The spacing is one wave length of themean frequency of the wave signals applied to the antennas for vascanning sector slightly less than 60 degrees.

The locating system also includes means for providing at least twocarrier-frequency wave signals having a substantially quadrature phaserelationship :and 'having a first frequency during alternate spacedintervals and a'second This means comprisesa carrier-frequency.wave-signal generator 14 Vand a conventional` QO-degree phase shifter 15which are operative during the aforesaid alternate or transmittinginter-`vals, and comprises a second carrier-frequency `wave-signal ,generator16 Vandanother 90-degree phase shifter A control unit 25 is coupled toboth" of the generators The unit 25 is of the type which generatesperiodic volt- --age pulses that are effective to place the generator 14in an operative condition and simultaneously to render the generator 16inoperative during transmitting intervals.

1.25 renders the generator 14.inoperative and the generator 16operative. The controlling action of the unit 25 is 'such that thegenerators 14 and 16 develop pulse-,modu- "lated carrier-frequency wavevsignals at a high repetition frate. i

The locating system further includes meansjfor. pro- `17` which areoperative during the aforesaid intervening 14 and 16 for controlling theoperation thereof duringL the aboveamentioned transmitting and receivingintervals.

However, during'the receiving intervals the unit 4 viding two modulationsignals having a substantially quadrature phase relationship and havinga frequency related to the desired frequency of scanning of theabovementioned predetermined space by `the radiant-signal beam. 'Ihisscanning frequency is preferably much less than the operatingfrequencyjof the unit 25 which controls the operation of the generators14 and `16. One of these last-mentioned means comprises a low-frequencymodulation-signal generator 20 and a 90-degree phase shifter 21 which iscoupled to the output circuit thereof. The generator 20 preferably has afrequency equal to the frequency of scanning by the radiant-signal beam.Another of the last-mentioned means comprises a modulation-signalgenerator 22 which develops a signal having a frequency equal to twicethe frequency of scanning, and a quadrature phase shifter 23 which iscoupled to the output circuit of the generator 22. The generators Z0and`22 areV closely synchronized inoperation by suitable means such asmutual coupling.

'I'he locating system also includes a wave-'signal receiver of thesuperheterodyney type. receiver includes aplur'ality of heterodynemodulators 30, 31, 31', 32, and 32 `coupled Vto individual ones of therespective antennasll), 11, 11', 12,` and 12 through conventionalduplexers 40, 41, 41', 42, and 42. These duplexers may be of the typedisclosed in United "States Letters Patent No. 2,415,318, grantedFebruary 4, `1947, to Harold A. Wheeler, entitled Wave-Signal `ReceiverArrangement, and assigned to the `sameiassignee as the presentinvention. Output circuits ofthe -heterodyne modulators are coupled toan` intermediate-frequency amplifier 33 through individualintermediate-frequency amplifiers `50, 51, 51', 52,` and S2 and theoutput circuit of the amplifier 33 is coupled to the control electrodeand cathode of a 'conventional cathode-raytube 34 through a detector andvideo-frequency amplifier 35. The cathode-ray tube 34 is energized inconventional manner, but a negative bias is applied to its controlelectrode normally to maintain the tube in the condition ofanode-current cutoff except when a signal is applied thereto from theunit 35. The cathode-ray tube 34 is provided witha pair of horizontaldeflecting electrodes 36, 36 which are supplied with sawtooth sweeppotentials from a horizontal sweep generator 37. In order that thehorizontal trace of the tube V34 as thus operated may provideindications of'the angular` direction ofra wave-signal reector withrespect to the axis of alignment ofthe antennas 10, .11, 11', 12, and12'-, synchronizing signalsffor controlling the loperation of the`generatorV 37` are supplied to the input circuit thereof from the nphaseshifter 211through a conductor 38. The tube 34 is also providedwith'lvertical deflecting electrodes 39,39` which "are suppliedwithlsaw-tooth sweep potentials from a verticali sweepgenerator44. As willpresently become `morefu'llyj apparent, the vertical trace -of the tube34 maybe calibrated in units of distance of -a `wave-signal `reflectorfromv thewl'ocating system.

The locating system lfurther includes modulator means jointly responsiveto the signals developed byttthe generators-14,-16, 20, and 22 andfthe.phase Shifters `associated therewith'for deriving and applying to the:antennas -rnentioned above, during transmittingintervals,` individ- 4ual.ones off axplurality of wave"-signal ymodulation components ofindividual different frequencies, (and for deriving. and applying to the1 above-mentioned'heterodyne modulators during `receiving intervalsyindividual ones of ithe. aforesaid plurality of wave-signal modulationcomponentsibut of individual'.frequenciesditferent `from each other andfro'mfthe first-mentioned.compdnents` This is -to permit thesystemangularly towscanpa predetermined -space with` apulse-modulatedradiant-signal beam. It -also permitsradiant-signalreiiergy kof .theLabeam reflected -by anyV 'radiant-signalreecton such sas an aiderait, in the aforesaid space" tothereceiving-translators `todproduce .in i the` heterodylne` modulatorsfn'iddulation i. components having l-additiv'e ,phaseonlyfomonei'direction V'of recep- `tapped and are-coupled together.

tion the receiving translators, which direction vscanstheulpredetermined ,spiace effectively Vin 'synchronism' 'with theradiant-signal beam; This `modulator 'means is of thesuppressed'carr'ier'type and is yresponsive to wave 'signalsandmodulation signalsV of predeterminedrelated amplitudes and having theparameters thereof so selected and output circuits so coupled to eachother that at least two Wave-signal modulation components of dilerentfrequencies are derived by` the lmodulator means. This modulator meanscomprises two pairs of conventional balanced modulators 55, 55 and 56,56 which form the modulator systems 57 and 58. These balanced modulatorsare generally similar in construction and each includesl a pair ,ofelectron tubes 59, 59. The carrierfrequency Wave'signalfromthe generator14 is 'applied through vtransformersftl, 60 in the same polarity to theinput circuits of the modulator tubes of each modulator stage.In-particular, thisy Wavesig'nal isapplieddirectly to the modulators 55'and 56' and through the phase Shifters 15 and v1S to the'respectivemodulators 55 and 56.*"Likewisegthe carrier-frequency` signal from thegenerator 16 is appliedy through transformers 61, 61 in thesamepolarityto the input circuits of the modulator tubes of'ea'ch modulator"stage,directly in the case of the modulators 55 and 56' and through the phaseshiftersV 17 .andi 19 tothe respective modulators 55 and 56. Themodulation signal from the lgenerator 20 is applied through aAtransformer 62 diiferc'antiallyv or in push-pull totheinputicircuits ofthe modulator tubes of modulators 55' and 55, thersignal being applied.directly to the modulatorV 55' i and through the phase shifter 21 tothe imodulator 55. .'=Likewise,'.-the modulation signal from thegenerator 22 is similarly applied to the tubes of. unit .58,tthroughtransformers 63, 63v and the phase shifter 23. v .`Each of themodulators includes an output transformer 6.4,;the primary winding 65 ofwhich is connected in pushpullfrelation to the;anodes of the tubes 59,59 thereof. Thefprimary windings-of the .transformers 64 are center- Thesecondary windings 66,66 ofthe transformers 64, 64 of the 'modulatingsystem 57 have, their relative numbers of lturns so proportioned and are.so coupled to each other in a common output circuit that lat `least twowave-signal modulation Vside-band--frequency components are derived, ina. manner to4 be explained subsequently, in the common output circuit ofthe modulators 55 and 55'. To this end, the vsecondary Winding of thetransformer 64 of the modulatorrSSHis center-tapped and so wound as to.develop twice the;voltage developed across the corresponding winding oftthe transformer 64 of the modulator 55. Furthermore, these secondarywindings are so poled and interconnected by way of'the center tap justmentioned that the voltage/developed across the left half of thesecondary EWinding of the transformer 64 of the vunit 55 adds to thatdeveloped across the secondary winding of the corresponding transformerof thepmodulator 55. Also, thevoltage developed across the right-,halfof the secondary winding of the transformer 64 of the modulator55,gsubtractsjfrom thatuproduced across the,V secondary Winding-Offhejitrjansforrner 64 of the ,modulator 55. secondary windings; of.the transformers ,64, 64 of the'y Imodulators y-56 and 56 are similarlylproportioned and connected. y,A conductor 67 couples one outputtervminal. Ofthesecondary winding 66 of modulator 55 to the duplexerA.41k andv another conductor 6,8 couples the other outputhterrnnalvthereof to the duplexer 41. Conductors 69hand -,701couple correspondingterminals of .the,secondary lwinding 66 lof the modulator 56 to therespetiveduplexers 42' @114,412..

l,gThev locating system also `includes means for applying high-powerenergizationgto, each ofl the described modulatorsrluringxtransmittingintervals of operation thereof andv means for. providing low-powerenergization therefor during-receiving ntervalsr The first-mentionedmeans ,am A. .i di

comprises a pulse modulator 72, the input circuit of which is coupled tothe control unit 25 and theoutput circuit of which is coupled to theprimary' winding of a transformer 73. The secondary winding of thetransformer 73 is coupled between the center" tap of the primary'winding of one of the transformers 64 and'ground through a source ofpotential, s uch as a battery74. .As will be made clear hereinafter, thebattery 74 supplies low-power energization for each of the modulatorsduring the receiving intervals of the systenL `An amplifier 75 includesan electron tube 76 which has an input circuit coupled by means oftransformers 77 and 78 to the respective output circuits of thecarri'erfrequency wave-signal generators 14 and-'16. Any outputtransformer 79 and a conductor 80 couple thev anode circuit of the tube76 to the duplexer 40.` The primary winding of the transformer 79couples the anode o f the tube 76 to the center tap of the primarywinding of a transformer 64. The input circuit ofthe vertical sweepgenerator 44 is also coupled to the center ltap of the primary windingof a transformer 64 through an attenuator 81 so that a vertical linearsweep from the bottom to the top of the screen of the cathode-raytube 34may occur at the pulse-repetition rate" of the pulse modulator 72;

The cathode-ray tube 34, which utilizes the additivephasemodulationcomponents lderived bythe receiver in a manner to be explainedsubsequently, provides anindication of the range of the reecting objectin space along the 'vertical axis of the cathode-ray tube screen and anindication of azimuth or direction along the horizontal axis thereof.'Ihe horizontal'deectionof the cathoderay tube'is preferably calibratedin terms of azimuth over the limits of the useful sector being scanned,namelyfa 60-degree sector for the antennaspacing mentioned above. Zeroazimuth is conveniently selected as normal tothe axis of the antennaarray. The vertical deflection mayY similarly be calibrated in terms ofdistance to a reflecting object. f

lConsidering now the operation of the locating system just described,the control unit 25 develops periodic control-voltage pulses at ahigh-repetition rate which are effective-'to establishthe transmittingand receiving intervals of the system. To promote anunderstandingthereof, the operation will be rst considered withreference to an alternate or transmitting interval and the nextsucceeding interval. During eachtransmitting interval, the generator 1'6isrendered. inoperative while the generator 14 is rendered operative bycontrol-Voltage pulses applied thereto from the unit 25. The-generator14 generates a carrier-frequency Wave signal E cos wt, or in thesimplerfnotatio'n vindicated on Fig. l'of the drawings, thesignaloffrequency f1. The control unit 25, during each transmittinginterval, also causes the pulse modulator 72 to generate and applythrough the transformer 73 a rvoltage pulse of Vlarge value which isAapplied to both modulator tubes o'f all of the modulators 55, 55', 56,and 56 and also to the anode of the tube 76 in the radiofrequencyamplifier 75. The latter amplies-the carrierfrequency wave signal f1 and-applies it through the duplexer 40' tothe antenna 10 for radiationthereby. The carrier-frequency signal f1 from the generator 14 is also-applied through individual ones of the ytransformers 60 to theinputcircuits of-the modulators 55,557,256, and 56'.' .The phaseShifters 15 and 18 aordV a 90-degree phase shift to 'the signaltranslated thereby as noted on Fig. lA of the drawings. The generators20 and 22cou.- tinuously and diiferentially apply Athe Vmodulationsignals thereof to the input circuits of .thel modulators of therespectivev systems 57 ,and 58` through the transformers 62 and 63. Thephase VShifters 21 Aand'23 likewise pro.- the modulation signalstranslated thereby. z u A. In a well-knownmanneneach of the modulators55, 55,', 56, and 56 isresponsive to -the.individua1,carrier aosaois'rfrequency and modulation signals applied thereto toy def velopy ,in itsoutput circuit a modulated carrier signal. f Further, and for rreasonswell known, each is effective rEu=the maximum amplitude of thewave-signal voltage applied to they antennas 11 or 11' w1=21rf1=theangular frequencyfof the carrier signal gen-y `erated by the generator14, and wh=21rfh=the angular frequency of the modulation signalgenerated byy ther generator y f f It canbe similarly shown that themodulator 55 f tothe secondary ywinding ofy itsy transformer 64 avoltage el', which may be expressed by the relation: f,

yeb=1/2E11 cos (wif-whM-l-l/zEn cos (-w-l-whh (2) Because of thepreviously describedfconnection of the secondary windings' of the outputytransformers of the W'modulators 55 yand 5S, the sum of these voltagesbetween ground and thecond'uctory 67 vhas the value: f

v e:nf-E11 CCS (wr-w10? and this resultantvoltage,v is lapplied totheantennav 11 through the conductor 67 and thefduplexer 41".' In sim'-yilar manner, the sum of the voltages between ground and the conductor68fl1as the value: f f t' ensFfErrCOS (w1+wh)l` f and is applied vtoltheyantenna y11 by means ofthe conductor 68 and the duplexer 411. Thus,it will 'be' seen thattheupper side-band frequency component is applied'tot the antenna llfwhillef the lower side-,band frequency component is'applied to the antenna 11'. Similarly, vfor ya `maximum amplitude E12 ofthe wave-signal voltage' applied to the antennas 12, 12' and for anangular frequency 2mb of the modulation signal of the generator 22, theupper side-band frequency component:

e'70:E12 C05 (wirt-2am `(5) and the lower side-band frequencycomponent:V @asf-E12 COS (wr-20m)t (6) are applied to therrespectiveantennas 12Vand 12.'.

It will be manifest that the frequency difference of the wave-signalmodulation components thus applied to any two adjacent antennas is equalto the frequency of the modulation signal produced by the generator 20,which frequency represents the frequency with which the system scans aVspace area with its radiated-signal beam or `with its antenna-systemdirective characteristic. It Will also be'appare'nt that theupperside-band modulation components are applied to those radiators onone'side of the central antenna 10, withthe components of increasingfrequency applied in vthe order of spacing of corresponding antennasfrom the latter, while the lower side-band modulation components areapplied to those radiators on the oppositeside of the central antenna,with the components of decreasing frequency applied in the order ofspacing of corresponding antennas from the antenna `10. Whentheantennasystem is excited withthe wavesignal modulation components inthe manner described mentioned United yStates yLetters :Patent No.y2,429,726. f The` radiated beamis the `sum of the voltages modified v ,ff yby the yspacingfand the directivity of the antennas 10,

i11,y 11', 12, and k12' andy may be expressedby they equaf +213, eos 2wht+21r cos s] cos w15 (7) where f(D)=a mathematical yexpression givingthe directivity yof an antenna element as a function of the angle ofradiationin a plane normal to the axis of alignment of such element andits `associated'reflector and measured f f from ysuch axis tEm=themaximum voltageapplied to the antenna 10 m=the angle scannedby'the'system measured relative 'to' f f the axis of alignment of theantennas `:the wave length of the carrier signal f1 d=the spacingbetween'radiators expressedasy affraction f y,of the wavelengthlt ltvcanfbe shown that rEquation 7fis that yfor a carrierfrequency signalmodulated in time and in direction v f f t rThe directionof scanning bythe radiantsignal beam is above, the directional radiationcharacteristic of the anangularly scans through an angle which, by theuse of t t`he tantenna relectors 113,' is vapproximately v6() degreeswide. SA? `detailedexplanation of radiant-signal beam scanning of thischaracter appears in applicants abovefrom the antenna having `the ywaveysignal of highest frequency -applied thereto to the antennahaving'the'signali f f of lowestrk frequency Vapplied thereto when theradiators yare energized as indicated'. t Shouldthe vorderof theconnections of the radiators ybe reversed from left to right, f t

however, the direction of scanning would also be` `reversed.

A radiant-signal reilector fwhich isr scanned bylther of this reflectedenergy is `the same as'ithatfof, the signal f applied to the antenna1l). This reilected wave'signal :is intercepted by, the yantennas ofVthe antenna system during a succeeding or receiving interval atfaltimetherein related to the round-trip propagation time between the locatingsystem and the reflector in space.

The control unit 25 terminates at the end of the rst alternate ortransmitting interval both the carrier-frequency signal developed by thegenerator 14 and the energizing pulse generated by the pulse modulator72, and at the same time applies a suitable control signal to thegenerator 16 thereby causing it to generate a carrier frequency signalexpressed by the relation:

or, as more simply expressed, a signal of frequency f2. Thiscarrier-frequency signal is thus generated during the receiving intervaland preferably has `a frequency lower than that of the signal f1. Thesignal f2 is applied to the radio-frequency amplifier 75 by thetransformer 78 and also is applied by the transformers 61, 61 to thebalanced4 modulators 55,` 55', 56, and 56'. The phase Shifters 17 and 19shift thephase of the signal translated thereby `90 degrees, but inthe`opposite direction to the phase shift afforded Vby the units `15 and18. `During the receiving interval, the generators 20 and 22 alsosupply'modulation signals to theseveral balanced modulators. Thecarrier-frequency signals developed by the modulator systems 57 and58"and the Vradio-frequency amplifier 75 during the receiving intervalhave a lowpower value since the` energization supplied by the battery74Vis considerably less than that afforded by the pulse modulatorf72throughthe transformer 73. The resultant -upper side-band and lowerside-,band `"modulation components are developed as rst described and'are applied to individualf ones `of the heterodyne modulators 30, V31,31, 32, and 32' through` thel.correspond ing duplexers. It can readilylbe shown that the fre- -1Whilefor simplicity quencies of the signalsapplied to the heterodyne modu- V vtenna system. 'I'he heterodynemodulators derive the heterodyne diierence-'frequency signal componentsand these are selectively amplied in the intermediate-frequencyamplifiers 50, S1, 51', 52, and 52. The signal output of thesey ampliersare applied to the combining intermediate-frequency amplifier '33. Itcan be shown that the resultant intermediate-frequency signal derivedduring the intervening interval may be expressed by the equation:

42E@ cos zQuhH-zvr cos where f3=the frequency of theintermediate-frequency signal developed in the intermediate-frequencyamplifier 33 Thus, it willbe seen that the foregoing equation isidenti-A cal with the Equation 7 for the signal transmitted by thelocating system except for the maximum voltage amplitude thereof, which-has a relatively low value during the receiving interval, andoexceptfor the frequency of the intermediate-frequency signal which isalsolower than the. signal transmitted during the transmitting interval.It therefore may be said that themodulation components produced in theheterodyne modulators have additive phase for only one direction ofreception by the radiators, which'directionscans the space in which thereflector is located effectively in'synchronism 'with the transmittedradiant-signal beam. i

The signalfoutput of the intermediate-frequency ampliier 33 isr detectedand amplified inthe usual manner by the unit 35` and is applied to the.input circuit of the cathode-ray tube 34. The synchronizing signalsderived during] thepreceding alternate interval from the 'units72 Aand'20', .control the operation of 'the horizontal sweep generator 37V yandthe. vertical sweep Vgenerator '44 ,and thefsweep' potentials producedbyy generators 37 vand 44 so'deect the cathode-ray beam of thecathode-ray tube 34' that the application of a derivedvreected signaltothe input circuit of ,the cathode-ray tube produces in thejwellknownmanneranindication ofthe distance and the direction of thev,wave-,signal reector in space; from 'the locating System, i f e v theoperationhasd been described generally: with reference yto .alternatetransmission intervals and intervening receivingintervals withoutmentioning the relative durations Vof these intervals, it will beunderstood that irl-practice the alternate transmitting intervals areofrelatively/ shortduration (for example, of the order oftone microsecond)while-the intervening reeiving intervals are of relatively much longerduration (forexample, 11000 microseconds) .so that eiectively shortpulses ofvwave-signal energy. are radiated at a highrepetition `rateduring the transmitting` intervals and resignal beam progresses throughonly a small angle. Hence, reflected energy from an object within ay mumpredetermined distance in space may be received before the receivingdirectivity of the system has changed appreciably. Sincefrequency-responsive devices such as band-pass networks, for selectingpredetermined ones of the plurality of closely spaced high-frequencywavesignals which are produced when low-scanning frequencies areemployed ina scanning system which electrically moves the scanning beam,are diicult to build but are unnecessary in the scanning system justdescribed, the latter is particularly'advantageous when the scanning isaccomplished 4at a low rate.

Referring now to Fig. 2 of the drawings, there is represented partlyschematically a modification of'a radiantsignal locating system which issimilar to that represented in Figs. l and 1A, correspondingelementsbeing designated by the same reference numerals. The system ofFig. 2 diiers from that of Fig. l in that the Vradiating system of Fig.2 -includes an even number of antennas, for example six, instead of theodd number of ve shown in Fig. 1. This change from an odd number ofantennas to an even number thereof changes somewhat the modulatorarrangement in that modulator 75 is now a balanced modulator of thecarrier suppressed type and applies upper side-band `and lowerside-bandvmodulation components to the spaced 'antennas 10 and 10through duplexers 40 and 40'. Further, the modulation signals which areapplied to the modulator systems 75', 57, 58 by the modulation-signalgenerators 20a, 20h, and' 2,0,l have frequencies /gfh, f/2fh, and zfh,and 'are'synchroniz'ed'by a voltage ofV frequency fh supplied by thegenerator 20, for reasons more fully explained in applicantsabove-mentioned Patent No. 2,426,460. f The operation of the Fig. 2locating system is essentially similar to that of the Fig. 1arrangement, except for the frequencies of the derived and transmittedWave signals, the modulation signals, and the signals applied to thereceiver portion of the system. It may be shown that the' radiant-signal4beam transmitted by the locating system of Fig;Y 2 may be expressed bythe equation: l

It4 may also be shown that the composite intermediatefrequency signalresulting from the heterodyning of the received-,reected'wave signal andthe signals developed by the modulator systems 75', 57and 58 vduring theintervening receiving intervals maybe expressed bythe equation: f

Both of these equations define a carrier WaveA which modulated in timeand in direction and are therefore ilec'ted'wavelsignalenergy sreceivedduring the longer receiving Kintervals. The pulsingj rate is"preferably suli-` ciently'higIiQlWith, relation Vto.thefangularfscanning frequency 'joff ltl 1je' A radiatedsignal beam'.that severalV wavellpulses aretradjafgd the scanning by theradiantsimilar in nature to the corresponding Equations 7 and 9 whichrepresent thetransmitted and the composite inter-,.-v mediate,frequencylsignals of the an'angementroffig'. 1.;

From'the"`foregoingfdescriptions of the two. embodiments'of theinvention,"it be apparent that a locating system iembodying 'the presentinvention is'adapted to scanna predeterminedspace entirely by vrativelysimpl' electrical and without the Vuse of cumbersome rotatingvmechanical apparatus; `The nature of the locating system -suchtthattheV scanning may -be accomplished with pulse-modulated wavesignals andat extremely lowscanning rates.4 The construction Vand the arrangementof the balanced modulators employed in the locating system` are suchthat they -render unnecessary the use of any expensive system ofwave-signal band-pass selectors for deriving wave signals of properfrequency for transmission and` reception, thus simplifyingrtheconstruction of the locating system and'materially reducing the costthereof. Furthermore, the same `balanced modulators may lne-employed forboth `transmission at a high-power level and for reception with normallow power applied to thetreceiver ofthe locating system. I-t will alsobe clear from the' Aforegoing description that the same radiating systemmay beemployed for both transmission and reception,jt hus effectingadditional economy. s

While there have been described what are at present considered to be thepreferred embodiments of this invention,it will ybe obvious to thoseskilled in the art that various changes and modilications may be madetherein without-departing from the invention, and it is, therefore,

aimed to cover all such` changes and modilications as fall t within thetrue spirit and scope of the invention. What is claimed is: f t l. Asystem for scanning -a predetermined space with a `radiant-signal beamcomprising: a plurality of spaced signal radiators; means for providingtwo carrier-frequency` wave signals having `a substantially quadraturephase relationship; means for providing two signals hav-1inga1,ssubstantially `quadrature phase relationship and having afrequency related to the desired frequency of scanning ofA saidpredetermined space by said radiantsignal beam; modulatorV meansresponsive to said wave signals and said signals for deriving atleasttwo wavesignal modulation components of different frequencies; and meansfor applying said derived components to individual ones of saidradiators, whereby said system angularly scans said predetermined spacewith said radiantsignal beam.

2. A system for `scanning a predetermined space with a radiant-signalbeam comprising: a plurality of spaced signal radiators; means forproviding two carrier-frequency wave signalshaving a substantiallyquadrature phase relationship; means for providing two modulationsignals having a 'substantially quadrature phase relationship andhavinga frequency related to the desired frequency of scanning of saidpredetermined space by said radiant-signal beam;` balanced modulatormeans responsive tosaidf wave signals and said modulation signals forderiving at leastftwowave-signal modulation components '3f`diife`re`r1t` frequencies; and"` means for applying said derivedcomponents tov individual ones ofsaid radiators, w

wherebysaid system angularly scans said predetermined space with saidradiant-signal beam. l

s 3. A system for `scanning ay predetermined space with a radiant-signalbeam comprising: a plurality of spaced signal radiators; means forproviding two carrier-frequency wave" signals having a substantiallyquadrature phase relationship; means for providing two modulation Ysignals having a-substantially quadrature phase relationship and Shavinga frequency related tothe desired frequency of scanning ofsaidrpredetermined space by said t t'luenciesjnd hmeans for applyingsaid derived side-band frequeney components tojndigidualones of,saidradiators 'whereby `s a`id"system angularly 'scans-:said.predetermined space with 'aid `radiant-signa-l, beam. -J l Q4, A,vsystefrn 'for sanning a predetermined spaeegwith Ia" raclijanft-signalbeam comprising; 'a plurality of spaced; t

quency `wave, signal and a second carrier-frequency Wave signalhaving asubstantially `quadrature `phase relationship with respect to said rstwave signal; means for providing a first modulation signal and ajsecondmodulation signal having a substantially quadrature phase relationshipwith respect to *saidI rst modulation signal, said modulation signalshaving a frequency `related `to the desired frequency of scanning ofsaid predetermined space by said radiant-'signal beam; balanced`modulator means including means for modulating said iirst Wave signalwith said first modulation signal and for modulating said second wavesignal with said second modulation signal and jointly responsive to bothmodulated wave signals for deriving at least two wave-signal modulationside-band frequency components of diiferent frequencies; and means forapplying said derived side-band frequency components to individualonesof said radiators, whereby said system angularly scans saidpredetermined space with said `radiant-signal beam. t-

5. A system for scanning a predetermined space with a radiant-signalbeam comprising: a plurality of spaced signal radiators; means forproviding two Vcarrier-frequency wave signals having a substantiallyquadrature phase relationship; `means for providing two modulationsignals having asubstantially quadrature phase relationship and having afrequency related to the desired frequency of scanning of saidpredetermined space by said radiant-signal beam; a pair of modulatormeans responsive to said wave signals and said modulation signals andincluding individual output circuits soi coupled to each other ras toderive `at least two wave-signal modulation components of differentfrequencies; and means for applying said `derived components toindividual ones of said radiators, whereby said system angularly scanssaid predetermined space with said radiant-signal beam.

6.` A system for scanning a predetermined space with Va radiant-signalbeam comprising: a plurality of `spaced signal radiators; means forproviding two carrier-frequency `wave signals having a substantiallyquadrature phase relationship; means for providing` two modulationsignals `having a substantially quadrature `phase relationship andhaving a frequency` related to the `desired frequency of scanning ofsaidpredetermined space by said radiant-signal beam; a pair of modulatormeans responsive to said wave signals ,and modulation signals oftpredetermined related `amplitudes and having parameters so selected andoutput circuits so coupled to each other that said modulator meansderives at least two Wave-signal modulation componentstof diiferent`frequencies; and

means for applying said derivedcomponents to individual ones tof'said-radiators, whereby said system angularly scans said predeterminedspace with said `radiant-signal beam.

7. A system for scanning a predetermined space with aradant-signal beamcomprising: `an odd 1number' of aligned equally spaced signal radiators;means for providing two carrier-frequency wave signals `having asubstantially quadrature phase relationship; means for-providing twomdulation signals having a sub'stantiallyquadrature phase`relationshipand having a `frequency related to the desired frequency ofscanningfof said predetermined ,"space by said radiant-signal beam;lmeans for` amplifying onef said two wave signals; modulator meansresponsive to said Awave signals and said modulation signals forderiving at least two wave-signal modulation components of 4differentfrequencies equally spaced in the frequency spectrum fromthe frequencyof said one wave signal; and means for ,applying to the center one ofsaid radiators said amplified wave signal and for applying toindividualones of the others of said radiators said derived componentswith the components oflinci'easirlgV` frequency applied "in orderl tosaid other'tr'adiators inthe order of thealigned positions ,of saidlother radiators from an vend radiatorthereof, whereby sadsystemangularlyscans said predetermined space with said radiant-signal beam.

8. A system for scanning a predetermined space with a radiant-signalbeam comprising: a plurality of aligned equally spaced signal radiators;means for providing two carrier-frequency Wave signals having asubstantially quadrature phase relationship; means for providing twomodulation signals having a substantially quadrature phase relationshipand having a frequency related to the desired frequency of scanning ofsaid predetermined space by said radiant-signal beam; modulator means ofthe suppressed carrier type responsive to said wave signals and saidmodulation signals for deriving upper side-band and lower side-bandmodulation components; means for applying said upper side-bandmodulation components indlividually to those radiators which arepositioned on one side of the center point of said radiators with themodulation components of increasing frequency applied in order to theradiators in the order of spacing thereof from said center point; andmeans for applying the lower sideband modulation components individuallyto those radiators which are positioned on the other side of said centerpoint with the modulation components of decreasing frequency applied inorder to the radiators in the order of spacing thereof from said centerpoint, whereby said system angnlarly scans said predetermined space withsaid radiant-signal beam.

9. A system for locating a radiant-signal reflector by scanning apredetermined space Ywith a pulse-modulated radiant-signal beamcomprising: a plurality of spaced signal "translators; means forproviding two carrierfrequency wave signals having a substantiallyquadrature phase relationship and having a `first frequency during.

alternate spaced intervals and a second frequency during interveningintervals; means for providing two modulation signals having aquadrature phase relationship and having a frequency related to the`desired frequency of scanning of said space by said radiant-signalbeam; a wave-signal receiver including a plurality of heterodynemodulators coupled to individual ones of a plurality ofV spacedreceiving translators; modulator means jointly responsive to said wavesignals and said modulation signals for deriving and applying to saidrst-mentioned translators during said alternate intervals individualones of a plurality of wave-signal modulation components of individualdifferent frequencies and for deriving and applying to said heterodynemodulators during said intervening intervals individual ones of aplurality of wavesignal modulation components of individual frequenciesdifferent from each other and from said first-mentioned components,whereby said system angularly scans said predetermined space with apulse-modulated radiantsignal beam and radiant-signal energy of saidbeam reilected by any radiant-signal reflector in said predeterminedspace to said receiving translators produces in said heterodynemodulators modulation components having additive phase only for onedirection of reception by said receiving translators which directionscans said predetermined space effectively in synchronism with saidradiantsignal beam; and means for utilizing said additive-phasemodulation components to provide an indication of at least the directionof said reflector with respect to said system.

10. A system for locating a radiant-signal reflector by scanning apredetermined space with a pulse-modulated radiant-signal beamcomprising: a plurality of spaced signal translators; means forproviding two carrierfrequency wave signals having a substantiallyquadrature phase relationship and having a irst frequency duringalternate spaced intervals and a second frequency during interveningintervals; means for providing two modulation signals having aquadrature phase relationship and having' a frequency related to thedesired frequency of scanning of said space by said radiant-signal beam;a Wave-signal receiver'including a plurality of heterodyne modulationcomponents of individual different-frequenaeeggse modulators coupled toindividual ones of a plurality of said translators; modulator meansjointly responsive to' cies and for deriving and applying to saidheterodyne modulators during said intervening intervals individual onesof a plurality of wave-signal modulation components of individualfrequencies different from each other and from said first-mentionedcomponents, whereby said system angnlarly scans said predetermined spacewith a pulse-modulated radiant-signal beam and radiant-signal energy ofsaid beam reected by any radiant-signal reiiector in said predeterminedspace to said translators produces in said heterodyne modulatorsmodulation components having additive phase only for one direction ofreception by the receiving ones of said translators which directionscans said predetermined space effectively in synchronism with saidradiant-signal beam; and means for utilizing said additive-phasemodulation components to provide an indication of at least thedirectionof said intervening. intervals; means', for providing twomodula-' tion signalshaving a quadrature phase relationship and having afrequency related to the desired frequency of scanning of said space bysaid radiant-signal beam; a wave-signal receiver including a pluralityof heterodyne modulators coupled to individual ones of a plurality ofspaced receiving translators; modulator means, including means forproviding high-power `energization therefor during saidalternateintervals and means for providing low-power energization therefor duringsaid intervening intervals, jointly responsive to said wave signals andsaid modulation signals for deriving and applying to said flrstmentionedtranslators during said alternate intervals individual ones of aplurality of wave-signal modulation components of individual differentfrequencies and for deriving and applying to said heterodyne modulatorsduring said intervening intervals individual ones of a plurality ofwave-signal modulation components of individual frequencies differentfrom each other and from said first-mentioned components, whereby saidsystem angnlarly scans saidpredetermined space with a highpowerpulse-modulated radiant-signal beam and radiantsignal energy of saidbeam reflected by any radiant-signal reflector in said predeterminedspace to said receiving translators produces in said heterodynemodulators modulation components having additive phase only for onedirection of reception by said receiving translators which directionscans said predetermined space effectively in synchronism with saidradiant-signal beam; and means for utilizing said additive-phasemodulation components intervening intervals; means for providing twomodulation signals having a quadrature phase relationship and having afrequency related to the desired frequency of scanning of `said space bysaid radiant-signal beam; a

wave-signal receiver including a plurality of heterodyne modulatorscoupled to individual ones of a plurality 0f signal l translators;ylmeans yforr providing' ktwo carrier l r l `frequency Wave-y signalshavingy a: Substantially quadrature' phaser relationship' and having ars'tt frequency during alternate spaced intervals land a secondfrequencyduringl i f f intervening intervals; ,means 'for providingtwo modula-y.tion 'signals having'aquadrature phase relationship' and -f A'han/,ingra Vrfrequency .relatedy .to Athe desired frequency 0f i f f scanning. oflsaid space' by ysaid' radiant-signal'. beam; la.

' spaced' lreceiving translators; Amodulator means jointly l responsive.to saidwave signals and said. modulationl sigv i nals for deriving .andapplying; to ysaid Arstn`1entioned .g translators during said alternate.intervals yindividual ones of la plurality ofi wave-signal modulation.components of f individual. different "frequencies :and for derivingian-di applying to said heterodyue modulatorsv during said'intermnedspace to said receiving translators'produees in terveuing intervalsindividual ones of a. plurality ofwave* l t #signall modulationcomponents `of yindividual frequencies different from each other andvfrom'saidiirst-mentioned.

-' components, whereby lsaid system angnlarly scans saidl predeterminedl `space with. a `pulse-modulated radiant-- signal beam. and-radiantesignal renergy of.' said beam reflected.' by lanyradiant-signall .reector iny said prede.

'said rlzieterodyne i modulators modulation. componentsl having additive`phaseonly fol-'one dircctionofreceptinn, 'f l f by said receivingtranslators which Adirection Yscans lsaidpredetermined rspaceeffectivelyin synchronisrn withsaidl rradiant-signall beam;` and means responsive.to the .operf f 1ation 'osaid second-mentioned'means :and said.y moduf'latorl means for lutilizing :said additive-phase modulation.

components to provide 2in-'indication of the distance. andy l thedirection of said reector with respectl to said system,l f i 13.A.systemfor' locating'arradiantsignal 'relector by l scanning apredetermined Aspace with vra ypulse-modulated. l

radiant-signally beam comprisingz. a plurality of; spacedwave-signalreceiver-including al plurality ofhe'terodyne odynemodulators during said intervening intervals. in-A i f dividual ones ofa plurality of', Wave-signal ymodulation .side-band frequency lcomponentsy -f of. individuall fre-fr "quencies.. different from said.iirst-mentionedcomponents, f lwhereby. said system angularlyscanssaid,predetermined.i f f space .with a- :pulse-modulatedradiant-signal bearn and L f radiant-.signal yenergy of. said ,beamreflected; by any -i radiant-signal lr-elector in ysaidl predeterminedspace to said receiving? translators produces :in said; heterodyne`rmodulators-modulation components having additive phase;

only `lfor one direction of reception r by rsaidl receiving fltranslators'y -whichr direction scans said` predetermined. Y .spaceyeffectively in synchronisrn .wthsaid rada1.1tsignal.y f f beam; andymeans for. utilizing saidv additive-phase 'modtil f f l lationcomponents :to provide anl indication of `at rleastA -the directionofl'said,reectorwithrespect to said system.y l

Y ryReferences Citedintlieiile oftl'iisfpatent.ly 'f l i :wif'f'UNITBDsTATEs.PATENTS +P"

